Design And Performance Evaluation Of An Integrated Miniature Single Stage Centrifugal Compressor And Permanent Magnet Synchronous Motor

An attempt has been made in this present work to design, fabricate and performance evaluate an integrated single stage centrifugal compressor and permanent magnet synchronous motor which is a key component of the reverse brayton cycle cryocooler. An off the shelf compressor – the driven and electric motor – the driver was not available commercially to suffice the requirements of the reverse brayton cryocooler. The integrated compressor-motor system was designed and tested with air as the working fluid at mass flow rate of 7.3 grams per sec, with a compression ratio of 1.58 and driven by a 2 KW permanent magnet synchronous motor at a design speed of 108,000 rpm. A permanent magnet synchronous motor rotor was designed to operate to operate over 200,000 rpm at 77 Kelvin temperature. It involved iterative processes involving structural, thermal and rotordynamic analysis of the rotor. Selection of high speed ceramic ball bearings, their mounting, fit and pre-load played prominent role. Attempts were made to resolve misalignment issues for the compressor – motor system, which had severe impact on the rotordynamic performance of the system and therefore losses at high speeds [15], [16]. A custom designed flexible coupler was designed and fabricated to run the compressor – motor system. An integrated compressor – motor system was an innovative design to resolve considerably several factors which hinder a high operational speed. Elimination of the coupler, reduction of number of bearings in the system and usage of fewer components on the rotor to increase the stiffness were distinct features of the integrated system. Several custom designed test-rigs were built which involved precision translation stages and angle brackets. Motor control software, an emulator, a DSP and a custom designed motor controller was assembled to run the motor. A cooling system was specially designed to cool the stator – rotor system. A pre-loading structure was fabricated to adequately pre-load the bearings. Flow measurement instruments such as mass flow meter, pressure transducers and thermocouples were used at several locations on the test rig to monitor the flow. An adjustable inlet guide vane was designed to control the tip clearance of the impeller

LOSSES IN HIGH SPEED PERMANENT MAGNET MACHINES USED IN MICROTURBINE APPLICATIONS

ABSTRACT High speed permanent magnet (PM) machines are used in microturbine applications due to their compactness, robust construction and high efficiency characteristics. These machines are integrated with the turbines and rotate at same speeds. This paper discusses in details losses in high speed PM machines. A typical PM machine designed for microturbine application is presented with its detailed loss calculations. Various loss verification methods are also discussed. INTRODUCTION Microturbines are small combustion turbines with typical outputs in the range of 20 kW to 500 kW. A typical system rotates over 40,000 rpm. One of the key enabling technologies for microturbines is the integral high speed electrical machines operating at same speeds as the turbines, eliminating mechanical gearboxes. The result is a very compact, high efficiency system that allows for ease of onsite installation. High speed permanent magnet (PM) machines are typically used in microturbine application due to their high power density and high efficiency characteristics. Good understanding of high speed PM machine characteristics especially its losses is critical to predict system performance and to ensure reliable operation

Miniature high speed compressor having embedded permanent magnet motor

A high speed centrifugal compressor for compressing fluids includes a permanent magnet synchronous motor (PMSM) having a hollow shaft, the being supported on its ends by ball bearing supports. A permanent magnet core is embedded inside the shaft. A stator with a winding is located radially outward of the shaft. The PMSM includes a rotor including at least one impeller secured to the shaft or integrated with the shaft as a single piece. The rotor is a high rigidity rotor providing a bending mode speed of at least 100,000 RPM which advantageously permits implementation of relatively low-cost ball bearing supports

Systems Design, Fabrication, and Testing of a High-Speed Miniature Motor for Cryogenic Cooler

The long-term storage of liquid hydrogen for space missions is of considerable interest to NASA. To this end, the Reverse Turbo-Brayton Cryocooler (RTBC) is considerably lighter than conventional designs and a potentially viable and attractive solution for NASA's long-term Zero-Boil-off (ZBO) hydrogen storage system for future space missions. We present the systems design, fabrication, and performance evaluation of the Permanent Magnet Synchronous Motor (PMSM) powering a cryocooler capable of removing 20 W of heat at 18 K with a COP of 0.005 and driven by two 2-kW permanent magnet synchronous motors operating at 200 000 rpm and at room temperature and 77 K. Structural, thermal, and rotordynamic aspects of system design are considered

Design Of A Superhigh-Speed Cryogenic Permanent Magnet Synchronous Motor

This paper presents the design and simulation of a superhigh-speed permanent magnet synchronous motor (PMSM) that operates in the cryogenic temperature of 77 K. The designed PMSM is used to drive a two-stage cryocooler for zero boil-off and long duration storage of liquid hydrogen systems. The paper addresses electromagnetic and thermal finite-element analysis, selection of materials for cryogenic applications, stress analysis, rotor dynamic analysis, and some tradeoffs used in the design. A prototype PMSM was built to verify the design methodology. © 2005 IEEE

Aerodynamics Performance Test Of A High-Speed Miniature Centrifugal Compressor

Reverse Turbo-Brayton cryocooler (RTBC) is a possible solution for NASA long term Zero-Boil-off (ZBO) hydrogen storage system for future space missions. RTBC cryocooler can have similar thermal efficiency as the current state-of-the-art LH2 cryocoolers with much less weight and size. The miniature helium compressor is the key component for this system, because it contributes the major portion in weight reduction. The present paper concentrates on the performance evaluation of an aerodynamically scaled miniature single-stage air compressor design, which is the first stage in the prototype of the future two-stage inter-cooled helium compressor. The single stage centrifugal compressor, designed by the authors, features a radial impeller, an axial diffuser driven by an integrated high speed permanent magnet synchronous motor run on ceramic ball bearings. In this paper, issues addressing performance of a miniature machine such as the present integrated single-stage centrifugal compressor and issues including thermal management, rotordynamics, effect of blade tip clearance, testing techniques are discussed. According to the test results, lhe design of the single stage was successful and established a solid base for the future two-stage helium compressor design. Copyright © 2007 by ASME

Mechanical And Rotordynamic Design, Fabrication And Testing Of A High-Speed Miniature Cryocooler Motor

An attempt has been made in this work to design, fabricate and performance evaluate a 2 kW permanent magnet synchronous motor operating at 200,000 rpm and at the temperature of both room temperature and 77 K. Structural, thermal and rotordynamic aspects were considered and models were developed on an iterative basis. Prototypes were fabricated and models were validated through experimental results. The PMSM motor/generator prototype was fabricated. At this stage, experimental results were obtained for the test set-up operating at 200,000 rpm and air at room temperature. Models developed were validated comparing to experimental results. Copyright © 2007 by ASME

Systems Design, Fabrication, And Testing Of A High-Speed Miniature Motor For Cryogenic Cooler

The long-term storage of liquid hydrogen for space missions is of considerable interest to NASA. To this end, the Reverse Turbo-Brayton Cryocooler (RTBC) is considerably lighter than conventional designs and a potentially viable and attractive solution for NASA\u27s long-term Zero-Boil-off (ZBO) hydrogen storage system for future space missions. We present the systems design, fabrication, and performance evaluation of the Permanent Magnet Synchronous Motor (PMSM) powering a cryocooler capable of removing 20W of heat at 18K with a COP of 0.005 and driven by two 2-kW permanent magnet synchronous motors operating at 200000rpm and at room temperature and 77 K. Structural, thermal, and rotordynamic aspects of system design are considered. Copyright © 2009 Dipjyoti Acharya et al

Mechanical and Rotordynamic Design, Fabrication and Testing of a High-Speed Miniature Cryocooler Motor,” 2007 ASME Turbo Expo

ABSTRACT An attempt has been made in this work to design, fabricate and performance evaluate a 2 kW permanent magnet synchronous motor operating at 200,000 rpm and at the temperature of both room temperature and 77 K. Structural, thermal and rotordynamic aspects were considered and models were developed on an iterative basis. Prototypes were fabricated and models were validated through experimental results. The PMSM motor/generator prototype was fabricated. At this stage, experimental results were obtained for the test set-up operating at 200,000 rpm and air at room temperature. Models developed were validated comparing to experimental results